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Science Ace- Thematic Studies By: Ng Aik Yang(20) 1A1

Science Ace- Thematic Studies By: Ng Aik Yang(20) 1A1. Dry Ice. What is dry ice?. Basically, dry ice is the solid form of carbon dioxide, which comprises of two oxygen atoms bonded to a single carbon atom. Properties of dry ice.

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Science Ace- Thematic Studies By: Ng Aik Yang(20) 1A1

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  1. Science Ace- Thematic StudiesBy: Ng Aik Yang(20) 1A1

  2. Dry Ice

  3. What is dry ice? • Basically, dry ice is the solid form of carbon dioxide, which comprises of two oxygen atoms bonded to a single carbon atom.

  4. Properties of dry ice • At temperatures above −56.4 °C , Carbon dioxide changes from a solid to a gas with no intervening liquid form, through a process called sublimation. • The opposite process is called deposition, where dry ice changes from the gas to solid phase. • At atmospheric pressure, sublimation or deposition occurs at −78.5 °C . • The density of dry ice varies, but usually ranges between about 1.4 and 1.6 g/cm3. • The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water or ice and leaves no residue as it changes state.

  5. History of Dry ice • The properties of solid carbon dioxide were discovered in the early twentieth century. • It was first produced commercially in the 1920s in the United States. • Until fairly recently, dry ice was often referred to as hot ice, a reference to the fact that when one touched the cold surface the hand felt burned.

  6. How is dry ice produced? • First, gases containing a high concentration of carbon dioxide are produced. • Such gases can be a byproduct of some other process, such as producing ammonia from nitrogen and natural gas, or large-scale fermentation. • Second, carbon dioxide-rich gas is pressurized and refrigerated until it changes into its liquid form. • Furthermore, the pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. • The extreme cold causes the liquid to solidify into a snow-like consistency. • Finally, the snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.

  7. How is dry ice produced?

  8. Uses of dry ice • Keeping food cold for a period of time • Some recent developments for its use include: -using the pellets in blasting or cleaning-transporting medical specimens such as hearts, limbs and tissues for reattachment and trasplantation.

  9. Fast facts about dry ice • No significant chemicals are created in the production of dry ice. • Dry ice can be used to loosen asphalt floor tiles or car sound deadening making it easy to pry off. • Dry Ice Bombs! Check this out – Dry Ice Bomb

  10. Liquid Nitrogen

  11. What is liquid nitrogen? • Liquid nitrogen is nitrogen in a liquid state at a very low temperature. • It is produced industrially by fractional distillation of liquid air. • Liquid nitrogen is a colourless clear liquid with density at its boiling point of 0.807 g/mL and a dielectric constant of 1.4.

  12. Properties of liquid nitrogen • At atmospheric pressure, liquid nitrogen boils at 77 K (−196 °C; −321 °F) and is a cryogenic fluid which can cause rapid freezing on contact with living tissue, which may lead to frostbite. • Liquid nitrogen freezes at 63 K (−210 °C; −346 °F). • When appropriately insulated from ambient heat, liquid nitrogen can be stored and transported, for example in vacuum flasks. • Here, the very low temperature is held constant at 77 K by slow boiling of the liquid, resulting in the evolution of nitrogen gas. • Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks.

  13. Uses of liquid nitrogen • store cells at low temperature for laboratory work • immersion freezing and transportation of food products • coolant for overclocking a central processing unit, a graphics processing unit, or another type of computer hardware • freezing water pipes in order to work on them in situations where a valve is not available to block water flow to the work area. • making ultra-smooth ice cream.

  14. Liquid Nitrogen is FUN! • Check these out:http://www.youtube.com/watch?v=DzNIJ7d3KR0 http://www.youtube.com/watch?v=MaxZwsqstFs&feature=related

  15. Now, what happens if you mix dry ice and liquid nitrogen? http://www.youtube.com/watch?v=ctPbhKldOgA

  16. Bibliography • http://www.madehow.com/Volume-7/Dry-Ice.html • http://inventors.about.com/od/dstartinventions/a/dry_ice.htm • http://en.wikipedia.org/wiki/Dry_ice • http://www.britannica.com/EBchecked/topic/172281/Dry-Ice • http://en.wikipedia.org/wiki/Liquid_nitrogen

  17. THE END Can someone turn on the heat?

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